Hyperspectral imaging in diabetes and peripheral vascular disease

ABSTRACT

The invention is directed to methods and systems of hyperspectral and multispectral imaging of medical tissues. In particular, the invention is directed to new devices, tools and processes for the detection and evaluation of diseases and disorders such as, but not limited to diabetes and peripheral vascular disease, that incorporate hyperspectral or multispectral imaging.

REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 60/667,677 entitled Hyperspectral Imaging inDiabetes, filed Apr. 4, 2005, and U.S. Provisional Patent ApplicationSer. No. 60/785,977 entitled Hyperspectral Imaging of Angiogenesis,filed Mar. 27, 2006 which is hereby incorporated by reference.

BACKGROUND

1. Field of the Invention

The invention is directed to methods and systems of hyperspectral andmultispectral imaging of medical tissues. In particular, the inventionis directed to new devices, tools and processes for the detection andevaluation of diseases and disorders such as diabetes and peripheralvascular disease that incorporate hypespectral/multispeatral imaging.

2. Background of the Invention

Diabetes afflicts an estimated 194 million people worldwide, affecting7.90% of Americans (over 21 million people) and 7.8% of Europeans.Between 85% and 95% of all diabetics suffer from Type 2 diabetes,although nearly 5 million people worldwide suffer from Type 1 diabetes,affecting an estimated 1.27 million people in Europe and another 1.04million people in the United States¹. Both Type 1 and Type 2 diabeticpatients are at higher risk for a wide array of complications includingheart disease, kidney disease (e.g. nephropathy), ocular diseases (e.g.glaucoma), and neuropathy and nerve damages to name a few². The feet ofdiabetic patients are at risk for a wide array of complications, whichare discussed below. Problems with the foot that affect the ambulatorynature of the patient are not only important from the standpoint ofphysical risk, but also convey an emotional risk as well, as theseproblems disrupt the fundamental independence of the patient by limitinghis or her ability to walk.

Peripheral arterial disease (PAD) affects primarily people older than55. There are currently 59.3 million Americans older than 55, and over12 million of them have symptomatic peripheral vascular disease. It isestimated that only 20% of all patients with PAD have been diagnosed atthis time. This represents a dramatically underpenetrated market.Although pharmacologic treatments for PAD have traditionally been poor,2.1 million nevertheless receive pharmacologic treatment for thesymptoms of PAD, and current diagnostic tests are not considered to bevery sensitive indicators of disease progression or response to therapy.Additionally, 443,000 patients undergo vascular procedures such asperipheral arterial bypass surgery (100,000) or peripheral angioplasty(343,000) annually and are candidates for pre and post surgical testing.One difficulty in diagnosing PAD is that in the general population, onlyabout 10% of persons with PAD experience classic symptoms ofintermittent claudication. About 40% of patients do not complain of legpain, while the remaining 50% have leg symptoms which differ fromclassic claudication.

Relying on medial history and physical examination alone isunsatisfactory. In one study, 44 percent of PAD diagnoses were falsepositive and 19 percent were false negative when medical history andphysical examination alone were used.³ For this reason, physicians havelooked for other means to help in providing diagnosis. As in the case ofdiabetic foot disease, current technologies have fallen short.Nonetheless, patients are frequently sent to peripheral vascularlaboratories for non-invasive studies. While the test results are knownto be inaccurate, these results do provide some additional informationto physicians for assistance in diagnosis or treatment decisions.

Another problem face by physicians is disease of the peripheral veins.Venous occlusive disease due to incompetent valves in veins designed toprevent backflow and deep vein thrombosis, results in venous congestionand eventually stasis ulcers. Approximately 70% of leg ulcers are due tovenous occlusion. Many of these ulcers are found at the medialmalleolus. The foot is generally swollen and the skin near the ulcersite is brownish in appearance.

Pathology

Diabetic feet are at risk for a wide range of pathologies, includingmicrocirculatory changes, peripheral vascular disease, ulceration,infection, deep tissue destruction and metabolic complications. Thedevelopment of an ulcer in the diabetic foot is commonly a result of abreak in the barrier between the dermis of the skin and the subcutaneousfat that cushions the foot during ambulation. This, in turn, can lead toincreased pressure on the dermis, resulting in tissue ischemia andeventual death, and ultimately result in an ulcer.⁴ There are a numberof factors that weigh heavily in the process of ulcerations⁵—affectingdifferent aspects of the foot—that lead to a combination of effects thatgreatly increase the risk of ulceration:⁶

-   -   Neuropathy—Results in a loss of protective sensation in the        foot, exposing patients to undue, sudden or repetitive stress.        Can cause a lack of awareness of damage to the foot as it be        occurs and physical defects and deformities⁷ which lead to even        greater physical stresses on the foot. It can also lead to        increased risk of cracking and the development of fissures in        calluses, creating a potential entry for bacteria and increased        risk of infection.⁸    -   Microcirculatory Changes—Often seen in association with        hyperglycemic damage⁹ Functional abnormalities occur at several        levels, including hyaline basement membrane thickening and        capillary leakage. On a histologic level, it is well known that        diabetes causes a thickening of the endothelial basement        membrane which in turn may lead to impaired endothelial cell        function.    -   Musculoskeletal Abnormalities—Include altered foot mechanics,        limited joint mobility, and bony deformities, and can lead to        harmful changes in biomechanics and gait. This increases        pressures associated with various regions of the foot.        Alteration or atrophy of fat pads from increased pressure can        lead to skin loss or callus, both of which increase the risk of        ulceration by two orders of magnitude.    -   Peripheral Vascular Disease—Caused by atherosclerotic        obstruction of large vessels resulting in arterial        insufficiency¹⁰ is common in the elderly populations and is yet        more common and severe in diabetics.¹¹ Diabetics may develop        atherosclerotic disease of large-sized and medium-sized        arteries, however, significant atherosclerotic disease of the        infrapopliteal segments is particularly common. The reason for        this is thought to result from a number of metabolic        abnormalities in diabetics, including high LDL and VLDL levels,        elevated plasma von Willebrand factor, inhibition of        prostacyclin synthesis, elevated plasma fibrinogen levels, and        increased platelet adhesiveness    -   Venous Disease—Caused by incompetent valves controlling backflow        between the deep veins and the more superficial veins or        thrombosis of the deep veins. Venous occlusions are typically        observed in the elderly who typically presented with swollen        lower extremities and foot ulcers typically at the medial        malleolus.

Previous studies have shown that a foot ulcer precedes roughly 85% ofall lower extremity amputations in diabetic patients^(12, 13) and that15% of all diabetic patients will develop a foot ulcer during the courseof their lifetimes.¹⁴ More than 88,000 amputations performed annually ondiabetics,¹⁵ and roughly an additional 30,000 amputations are performedon non-diabetics, mostly related to peripheral vascular disease.Estimations have shown that between 2-6% of diabetic patients willdevelop a foot ulcer every year^(13, 16) and that the attributable costfor an adult male between 40 and 65 years old is over $27,000 (1995 USdollars) for the two years after diagnosis of the foot ulcer.¹⁶ Inconjunction with the increased total costs of care, Ramsey et al showedthat diabetic patients incurred more visits to the emergency room (morethan twice as many as control patients), more outpatient hospital visits(between 2× and 3× as many as control subjects) and more inpatienthospital days (between 3× and 4× as many as control patients) during thecourse of an average year.

Foot pathology is major source of morbidity among diabetics and is aleading cause of hospitalization. The infected and/or ischemic diabeticfoot ulcer accounts for about 25% of all hospital days among people withdiabetes, and the costs of foot disorder diagnosis and management areestimated at several billion dollars annually.^(16, 17)

Current Diagnostic Procedures

The first step in the assessment of the diabetic foot is the clinicalexamination^(18, 19). All patients with diabetes require a thoroughpedal examination at least once a year, even without signs ofneuropathy. Evaluation of the diabetic patient with peripheral vasculardisease should include a thorough medical history, vascular history,physical examination, neurologic evaluation for neuropathy and athorough vascular examination.²⁰

The next step in the work up of a patient with significant peripheralvascular or diabetic foot disease is non-invasive testing.²¹ Currentclinical practice can include ankle brachial index (ABI), transcutaneousoxygen measurements (TcPO2), pulse volume recordings (PVR) and laserDoppler flowmetry. All of these clinical assessments are highlysubjective with significant inter- and intra-observer variabilityespecially in longitudinal studies. None of these methods arediscriminatory for feet at risk, and none of them provide anyinformation about the spatial variability across the foot. Dopplerultrasound with B-mode realtime imaging is typically used to diagnosedeep vein thrombosis while photo and air plethysmography are used tomeasure volume refill rates as a means of locating and diagnosingvalvular insufficiency. Currently there is no method to accuratelyassess the predisposition to serious foot complications, to define thereal extent of disease or to track the efficacy of therapeutics overtime.

Background of Hyperspectral Imaging

HSI or hyperspectral imaging is a novel method of “imaging spectroscopy”that generates a “gradient map” of a region of interest based on localchemical composition. HSI has been used in satellite investigation ofsuspected chemical weapons production areas²², geological features²³,and the condition of agricultural fields²⁴ and has recently been appliedto the investigation of physiologic and pathologic changes in livingtissue in animal and human studies to provide information as to thehealth or disease of tissue that is otherwise unavailable.²⁵ MHSI formedical applications (MHSI) has been shown to accurately predictviability and survival of tissue deprived of adequate perfusion, and todifferentiate diseased (e.g. tumor) and ischemic tissue from normaltissue.²⁷

Spectroscopy is used in medicine to monitor metabolic status in avariety of tissues. One of the most common spectroscopic applications isin pulse oximetry, which utilize the different oxyhemoglobin (oxyHb) anddeoxyhemoglobin (deoxyHb) absorption bands to estimate arterialhemoglobin oxygen saturation.²⁸ One of the drawbacks of these systems isthat they provide no information about the spatial distribution orheterogeneity of the data. In addition, these systems report the ratioof oxyHb and deoxyHb together losing diagnostic information that can begarnered by evaluating the state of the individual components. Suchspatial information for the individual components and the ratio isprovided by HSI, which is considered a method of “imaging spectroscopy”,where the multi-dimensional (spatial & spectral) data are represented inwhat is called a “hypercube.” The spectrum of reflected light isacquired for each pixel in a region, and each such spectrum is subjectedto standard analysis. This allows the creation of an image based on themetabolic state of the region of interest (ROI).

In vivo, MHSI has been used to demonstrate otherwise unobserved changesin pathophysiology. Specific studies have evaluated the macroscopicdistribution of skin oxygen saturation,²⁹ the in-situ detection of tumorduring breast cancer resection in the rat,²⁷ the determination of tissueviability following plastic surgery & burns,^(30, 31) claudication andfoot ulcers in diabetic patients,³²⁻³⁷ and applications to shock andlower body negative pressure (LBNP) in pigs and humans,respectively.³⁸⁻⁴⁰ In a skin pedicle flap model in the rat, tissue thathas insufficient oxygenation to remain viable is readily apparent fromlocal oxygen saturation maps calculated from hyperspectral imagesacquired immediately following surgery; by contrast, clinical signs ofimpending necrosis do not become apparent for 12 hours after surgery.⁴¹

Non-invasive measurements of oxygen or blood flow have been demonstratedpreviously, with investigators using thermometry,⁴² point diffusereflectance spectroscopy,^(43, 44) and laser Doppler imaging.⁴⁵Sheffield et al, have also reviewed laser Doppler and TcPO₂ measurementsand their specific applications to wound healing.⁴⁶ While othertechniques have been utilized in both the research lab and the clinicand have the advantage of a longer experience base, MHSI is superior toother technologies and can provide predictive information on the onsetand outcomes of diabetic foot ulcers, venous stasis ulcers andperipheral vascular disease.

Because MHSI has the ability to show anatomically relevant informationthat is useful in the assessment of local, regional and systemicdisease. This is important in the assessment of people with diabetesand/or peripheral vascular disease. MHSI shows the oxygen delivery andoxygen extraction of each pixel in the image collected. These imageswith pixels ranging from 20 microns to 120 microns have been useful inseveral ways. In the case of systemic disease, MHSI shows the effects onthe microcirculation of systemic diabetes, smoking, a variety ofmedications such as all of the classes of antihypertensives (ACEinhibitors, ARBs, Beta blockers, Peripheral arterial and arteriolardilators), vasodilators (such as nitroglycerine, quinine, morphine),vasoconstrictors (including coffee, tobacco, pseudephedrine, Ritalin,epinephrine, levophedrine, neosynepherine), state of hydration, state ofcardiac function (baseline, exercise, congestive heart failure),systemic infection or sepsis as well as other viral or bacterialinfections and parasitic diseases. The size of the pixels used isimportant in that it is smaller than the spacing of the perforatingarterioles (˜0.8 mm)⁴⁷ of the dermis and therefore permits thevisualization of the distribution of mottling or other patternsassociated with the anatomy of the microcirculation and its responses.In the case of the use of MHSI for regional assessment, in addition tothe above systemic effects at play, the image delivers information aboutthe oxygen delivery and oxygen extraction for a particular region as itis influenced by blood flow through the larger vessels of that region ofthe body. For example an image of the top of the foot reflects both thesystemic microvascular status and the status of the large(macrovascular) vessels supplying the leg. This can reflectatherosclerotic or other blockage of the vessel, potential injury to thevessel with narrowing, or spasm of some of the smaller vessels. It canalso reflect other regionalized processes such as neuropathy or venousocclusion or compromise or stasis. In the case of local disease MHSIshows the actual effect of the combination of systemic, regional andlocal effects on small pieces of tissue. This combines the effects ofsystemic and regional effects described above with the effects of localinfluences on the tissue including pressure, neuropathy, localized smallvessel occlusion, localized trauma or wounding, pressure sore,inflammation, and wound healing. Angiogenesis during wound healing isreadily monitored with MHSI.

Wounds other than on the foot can be similarly assessed, such as sacraldecubiti, other areas of pressure necrosis, prosthesis stumps, skin flaptissue before, after or during surgery, areas of tissue breakdown aftersurgery, and burn injuries. Current optical methods for evaluatingtissues for the conditions described above include:

-   -   Laser Doppler (LD)—In early iontophoresis experiments as well as        recent efforts both LD and MHSI data were collected, and some        changes in our images (total hemoglobin) are primarily a        consequence of changes in perfusion which was roughly correlated        to LD. However, important other changes in MHSI images that        report specifically O₂ extraction and tissue metabolism (O2Sat)        are not related to perfusion or LD readings per-se. Superior        spatial resolution with MHSI, and O₂ extraction information adds        highly important clinical information.    -   Transcutaneous PO₂ (TcPO₂)—TcPO₂ data collected in subjects with        peripheral vascular disease and ischemia study as well as in        patients with diabetes both with and without foot ulcers. TcPO₂        measurements appeared cumbersome, lengthy (˜20-30 minutes),        highly operator dependant, and carried data only from skin        directly under the probe (with little ability to distinguish the        spatial characteristics of the ischemic area). While TcPO₂ has        been shown to carry statistically significant information in        terms of quantifying tissue at risk for ulceration,⁴⁸ TcPO₂ was        not encouraging as a useful clinical device.    -   Non-imaging techniques—Techniques such as near-infrared        absorption spectroscopy (NIRS) or TcPO₂, rely on measurements at        a single point in tissue which may not accurately reflect        overall tissue condition or provide anatomically relevant data,        and probe placement on the skin can alter blood flow and cannot        deliver accurate information in the area of an ulcer or directly        surrounding it. Because MHSI is truly remote sensing, data are        acquired at a distance, eliminating probe placement errors and        allowing the investigation of the wound itself, which some        techniques can not accomplish due to infection risk.        In short, analysis supports the following conclusions:    -   1. Level of oxygenated hemoglobin in the tissue of arms and feet        of diabetic subjects is lower than the level of oxygenated        hemoglobin in the skin of control subjects. This is        statistically significant result with separation between        diabetics and controls    -   2. Oxyhemoglobin in the arms and feet of ulcerated subjects is        lower than oxyhemoglobin in diabetics without the ulceration.        The strong signal suggests ability to distinguish diabetics at        lower and high risk.    -   3. Oxygen saturation level in the skin of arms and feet of        diabetics is lower than oxygen saturation in the skin of        controls. This is at a statistically significant level allowing        separation between diabetics and controls.    -   4. MHSI quantitatively assesses different areas of tissue        metabolism on both dorsal and plantar foot surfaces of any        curvature.    -   5. MHSI evaluates state of tissue as a function of distance away        from ulcer to assess the viability of surrounding tissue, and        evaluate the degree of risk of further ulceration.    -   6. MHSI can be classified with a 4-quadrant system to determine        the metabolic state of tissue using oxygen delivery and oxygen        extraction: low/low, low/high, high/high, and high/low. This        metric is used in distinguishing healthy tissue from ulcerated,        or from a tissue at risk of ulceration.    -   7. MHSI is a unique visualization method that produces an image        that combines spatial information from three independent        parameters characterizing tissue: oxygenated and deoxygenated        hemoglobin concentrations and light absorption.    -   8. MHSI evaluates skin metabolism at high resolution of 20-120        microns per image pixel.    -   9. Specific MHSI regions associated with the margins of the        ulcer correlate to inflammation (and/or infection).    -   10. Areas of decreased MHSI indicate tissue at risk for        non-healing, ulcer extension, or primary ulceration.    -   11. MHSI differentiates between regions of tissue associated        with a present foot ulcer on the basis of biomarkers such as        oxyHb and deoxyHb coefficients.    -   12. MHSI evaluates temporal changes in oxygen delivery and        extraction to particular areas, both, on local and systemic        scale. The trend in the change of oxyHb and deoxyHb are used to        predict healing status of a wound/ulcer as well as progression        of diabetic complications.    -   13. Specific results from MHSI are indicative of inflamed        tissue.    -   14. MHSI examines tissue for gross features that may be        indicative of global risks of complications, such as poor        perfusion or the inability of the microcirculation to react and        compensate in tissue.    -   15. MHSI has potential in diagnosing global microcirculatory        insufficiencies and impacting on other complications of diabetes        associated with the microvasculature besides foot ulcers.

MHSI is superior to other modalities for assessing the healing potentialof tissue adjacent to ulcers. MHSI provides more direct measurements ofoxyHb and deoxyHb activities of the affected tissue. Hence, thediscrimination is not markedly improved by adding iontophoresis resultsto refine prediction as is required for Laser Doppler to do so. MHSI hassignificant advantages over laser Doppler and TcPO₂ measurements.Whereas MHSI is able to deliver spatially relevant data with highspatial resolution, TcPO₂ delivers only single point data. Laser Dopplerdata has poor spatial resolution and is frequently reported as a singlemean numerical value across the region of interest.

SUMMARY OF INVENTION

The present invention overcomes the problems and disadvantagesassociated with current strategies and designs, and provides new toolsand methods for detecting tissue at risk of developing into an ulcer,for detecting problems with diabetic foot disease, and for evaluatingthe potential for wounds to heal.

One embodiment of the invention is directed to a medical instrumentcomprising a first stage optic responsive to illumination of tissue, aspectral separator, one or more polarizers, an imaging sensor, adiagnostic processor, a filter control interface, a general purposeoperating module to assess the state of tissue in diabetic subjectsfollowing a set of instructions, and a calibrator. Preferably, theinstrument further comprises a second stage optic responsive toillumination of tissue. Preferably, the set of instructions comprisespreprocessing hyperspectral information, building a visual image,defining a region of interest in tissue, converting the visual imageinto units of optical density by taking a negative logarithm of eachdecimal base, decomposing a spectra for each pixel into severalindependent components, determining three planes for an RGB pseudo-colorimage, determining a sharpness factor plane, converting the RGBpseudo-color image to a hue-saturation-value/intensity image having aplane, adjusting the hue-saturation-value/intensity image plane with thesharpness factor plane, converting the hue-saturation-value/intensityimage back to the RGB pseudo-color image, removing outliers beyond astandard deviation and stretching image between 0 and 1, displaying theregion of interest in pseudo-colors; and characterizing a metabolicstate of the tissue of interest.

Preferably, the region of interest is one of a pixel, a specified regionor an entire field of view. Preferably, determining three planes for anROB pseudo-color image comprises one or more characteristic features ofthe spectra, determining a sharpness factor plane comprises acombination of the images at different wavelengths, removing outliersbeyond a standard deviation comprises three standard deviations,displaying the region of interest in pseudo-colors comprises one ofperforming one in combination with a color photoimage of a subject, inaddition to a color photo image of a subject, and projecting onto thetissue of interest.

Preferably, defining the color intensity plane as apparent concentrationof one or a mathematical combination of oxygenated Hb, deoxygenated Hb,and total Hb, oxygen saturation, defining the color intensity plane asreflectance in blue-green-orange region, adjusting the hue saturationcomprises adjusting a color resolution of the pseudo-color imageaccording to quality of apparent concentration of one or a mathematicalcombination of oxygenated Hb, deoxygenated Hb, and total Hb, oxygensaturation, adjusting the hue saturation further comprises one or acombination of reducing resolution of hue and saturation color planes bybinning the image, resizing the image, and smoothing the image throughfiltering higher frequency components out, and further interpolating thesmoothed color planes on a grid of higher resolution intensity plane.

Another embodiment of the invention is directed to a method forassessing the state of tissue of a diabetic subject comprising,preprocessing hyperspectral information, building a visual image,defining a region of interest in tissue, converting the visual imageinto units of optical density by taking a negative logarithm of eachdecimal base, decomposing a spectra for each pixel into severalindependent components, determining three planes for an RGB pseudo-colorimage, determining a sharpness factor plane, converting the ROBpseudo-color image to a hue-saturation-value/intensity image having aplane, adjusting the hue-saturation-value/intensity image plane with thesharpness factor plane, converting the hue-saturation-value/intensityimage back to the ROB pseudo-color image, removing outliers beyond astandard deviation and stretching image between 0 and 1, displaying theregion of interest in pseudo-colors; and characterizing a metabolicstate of the tissue of interest.

Preferably, the region of interest is one of a pixel, a specified regionor an entire field of view. Preferably, determining three planes for anRGB pseudo-color image comprises one or more characteristic features ofthe spectra, determining a sharpness factor plane comprises acombination of the images at different wavelengths, removing outliersbeyond a standard deviation comprises three standard deviations,displaying the region of interest in pseudo-colors comprises one ofperforming one in combination with a color photoimage of a subject, inaddition to a color photo image of a subject, and projecting onto thetissue of interest.

Preferably, defining the color intensity plane as apparent concentrationof one or a mathematical combination of oxygenated Hb, deoxygenated Hb,and total Hb, oxygen saturation, defining the color intensity plane asreflectance in blue-green-orange region, adjusting the hue saturationcomprises adjusting a color resolution of the pseudo-color imageaccording to quality of apparent concentration of one or a mathematicalcombination of oxygenated Hb, deoxygenated Hb, and total Hb, oxygensaturation, adjusting the hue saturation further comprises one or acombination of reducing resolution of hue and saturation color planes bybinning the image, resizing the image, and smoothing the image throughfiltering higher frequency components out, and further interpolating thesmoothed color planes on a grid of higher resolution intensity plane.

Other embodiments and advantages of the invention are set forth in partin the description, which follows, and in part, may be obvious from thisdescription, or may be learned from the practice of the invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1: Block diagram depicting a portable hyperspectral imagingapparatus.

FIG. 2: Basic specifications of the MHSI system.

FIG. 3: OxyHb and DeoxyHb HSV/I color chart. Schematic representation ofthe MHSI display (left) showing the interplay between the oxyHb anddeoxyHb coefficients and describing some of the potential physiologicalconsequences of values of the MHSI.

FIG. 4: Representative data from dorsal surface of foot showingindividual oxyHb and deoxyHb values and how they can be used to evaluateregions of the tissue.

FIG. 5: Representative data from tissue showing sensitivity of MHSI todrug-induced changes in the vasculature. (left to right) Visible imageof foot surface post iontophoresis (IP), representative spectra pre andpost iontophoresis with Acetylcholine (IP) showing greater oxyHb levelsafter IP. Images of increased oxyHb coefficient ring where IP occurred,image of deoxyHb, showing little change post IP.

FIG. 6: Representative data from an ulcer located on the sole (ulcer 1)and dorsal surface (ulcer 2) of the foot.

FIG. 7: MHSI information from the soles and dorsal surfaces of fourpatients. Each row of images represents data from one patient. The twocolumns on the left represent data from the soles of the feet, while thecolumns on the right represent data from the dorsal surfaces of thefeet.

FIG. 8: MHSI image of diabetic foot ulcer with 200 segment radialprofile.

FIG. 9: MHSI of wounds during healing.

FIG. 10: color image (a) and pseudo-color image (b) of a rabbit ear

DESCRIPTION OF THE INVENTION

The major clinical advantage of hyperspectral imaging is the delivery ofmetabolic information derived from the tissue's spectral properties inan easily interpretable image format with high spatial resolution. This2-D information allows gradients in biomarker levels to be assessedspatially. Multiple images taken over time allow the gradient to bemeasured temporally. This adds new dimensions to the assessment ofulceration risk and tissue healing in that it will allow the physicianto target therapy and care to specific at risk areas much earlier thanpreviously possible. The reporting of biomarkers such as oxyHb anddeoxyHb levels in tissue individually and in an image format wherespatial distributions can be assessed has not been done before.Typically the two numbers are combined in a ratio and reported aspercent hemoglobin oxygen saturation (O₂Sat). MHSI has the clearpotential to be developed into a cost effective, easy to use, turn-keycamera-based metabolic sensor given the availability and relatively lowprice of components.

Surprisingly, MHSI information according to this invention can be usedto predict the onset of foot ulcers before there are clinicalindications, and provides early detection, diagnosis, and quantificationof progression of microcirculatory complications such as neuropathy indiabetic patients. For patients with foot ulcers, MHSI technology canevaluate the ulcer and surrounding area to predict whether that willheal or require surgical intervention. The present invention alsoprovides MHSI that is useful in the prediction and monitoring ofperipheral venous disease including venous ulcers.

There are many advantages to using MHSI. Not only does MHSI provideanatomically relevant spectral information, its use of spectral data ofreflected eletro-magnetic radiation (ultraviolet—UV, visible, nearinfrared—NIR, and infrared—IR) provides detailed tissue information.Since different types of tissue reflect, absorb, and scatter lightdifferently, in theory the hyperspectral cubes contain enoughinformation to differentiate between tissue types and conditions. MHSIis more robust than conventional analyses since it is based on a fewgeneral properties of the spectral profiles (slope, offset, water,oxyHb, deoxyHb, and its ratio) and is therefore flexible with respect tospectral coverage and not sensitive to a particular light wavelength.MHSI is faster than conventional analyses because it uses fast imageping techniques that allow superposition of absorbance, scattering, andoxygenation information in one pseudo-color image. Visible MHSI isuseful because it clearly depicts oxyHb and deoxyHb which are important,physiologically relevant biomarkers in a spatially relevant fashion.Similarly, NIR shows water, oxyHb and deoxyHb.

The simplicity of the presented false color images representingdistribution of various chemical species, either singly or incombination (such as ratioed), or in other more sophisticated imageprocessing techniques allow for the display of results in real tonear-real time. Another advantage of MHSI is easy interpretation. Colorchanges show the different tissue types or condition, but thedistinction is not a yes/no type. MHSI color scheme allows the surgeonor podiatrist to differentiate between different tissue types andstates. In addition, the color and the shape of structures depictdifferent composition and level of viability of the tissue. The data isthen represented in a developed MHSI standard format. OxyHb and deoxyHbare presented in a format similar to a blood pressure reading that iseasy for physicians to understand. Additionally, a tissue oxygensaturation value denoted as S_(HSI)O₂ is also provided.

MHSI main purposes include 1) expand human capabilities beyond theordinary array of senses; 2) expand the human brain capabilities bypre-analyzing the spectral characteristics of the observable subject; 3)perform these tasks with real or near-real time data acquisition. Insummary, the aim of MHSI is to facilitate the diagnosis and assessmentof the metabolic state of tissue.

Results of analysis have to be presented in an easily accessible andinterpretable form. MHSI delivers results in an intuitive form bypairing MHSI pseudo-color image with a high quality color picturecomposed from the same hyperspectral data. Identification and assessmentof a region of interest (ROI) is easily achieved by flipping betweencolor and MHSI images, and zooming onto the ROI. The images can be seenon a computer screen or projector, and/or stored and transported as anyother digital information, and/or printed out. The MHSI image preservesthe high resolution of the hyperspectral imager thereby allowing furtherimprovement with upgraded hardware.

Additionally, MHSI transcribes vast 3D spectral information sets intoone image preserving biological complexity via millions of color shades.The particular color and distinct shape of features in the pseudo-colorimage allow discrimination between tissue types such as ulcers, callus,intact skin, hematoma, and superficial blood vessels.

Initially, the algorithm presents oxyHb, deoxyHb and S_(HSI)O₂ to theuser to conclude characteristics of the tissue including, but notlimited to, discerning whether the tissue is healing or whether it is ata high risk of ulceration. In another embodiment, a particular colorcode contains adequate information for diagnosis and is presented assuch. In one iteration, MHSI by itself is not a definite decision makingalgorithm; it is a tool that a medical professional can use in order togive a confident diagnosis. In another iteration, MHSI contains adecision making algorithm that provides the physician with a diagnosis.

Due to the complexity of the biological system, medical personnel desireas much information as possible in order to make the most-reliablediagnosis. MHSI provides currently unavailable information to thedoctor, preferably to be used in conjunction with other clinicalassessments to provide an accurate diagnosis. MHSI provides images forfurther analysis by the user. As more information is gathered, aspectral library is preferably compiled to allow MHSI to be a truediagnostic device.

MHSI is preferably used to quantify medical therapies in order tomeasure the effectiveness of new therapeutic agents or procedures. Forexample, in wound healing studies, a typical subject population can bebroken down into one of three groups: those that will heal independentof therapy, those that will not heal independent of therapy, and theborderline cases that may benefit from the therapy. MHSI preferably isused to select borderline subjects for these studies where the treatmentif effective most likely benefits the subject. MHSI is used to quantifywound progression or prevention in order to identify new therapeuticagents and to develop individual therapeutic regiments depending onsubject response.

One embodiment of the invention is directed to a medical instrumentcomprising a first-stage optic responsive to illumination of a tissue, aspectral separator, one or more polarizers, an imaging sensor, adiagnostic processor, a filter control interface, and a general-purposeoperating module (FIG. 1). Preferably, the spectral separator isoptically responsive to the fist-stage optic and has a control input,the polarizer filters a plurality of light beams into a plane ofpolarization before entering the imaging sensor, the imaging sensor isoptically responsive to the spectral separator and has an image dataoutput, the diagnostic processor comprises an image acquisitioninterface with an input responsive to the imaging sensor and one or morediagnostic protocol modules wherein each diagnostic protocol modulecontains a set of instructions for operating the spectral separator andfor operating the filter control interface, the filter control interfacecomprises a control output provided to the control input of the spectralseparator, which directs the spectral separator independently of theillumination to receive one or more wavelengths of the illumination toprovide multispectral or hyperspectral information as determined by theset of instructions provided by the one or more diagnostic protocolmodule, and the genera-purpose operating module performs filtering andacquiring steps one or more times depending on the set of instructionsprovided by the one or more diagnostic protocol modules.

The instrument may also comprise a second-stage optic responsive toillumination of the tissue. Preferably, the one or more wavelengths ofillumination are one or a combination of UV, visible, NIR, and IR. Inpreferred embodiments, the multispectral or hyperspectral informationdetermines one or more of the metabolic state of tissue to assess areasat high risk of developing into a foot ulcer or other wounded tissue toassess the potential of an ulcer or the tissue to heal. Preferredembodiments include multispectral or hyperspectral information gatheredremotely and noninvasively. Alternatively, an imaging system could beaffixed to a wounded area to track its progress over time. Such a systemcould be attached to or embedded in a dressing, skin covering or adevice used to impact wound healing or maintain tissue integrity such asa vacuum suction system or a bed upon which a patient is lying or ashoe, boot or offloading device.

Another embodiment is directed to the set of instructions comprising:preprocessing the hyperspectral information, building a visual image,defining a region of interest of the tissue, converting allhyperspectral image intensities into units of optical density by takinga negative logarithm of each decimal base, decomposing a spectra foreach pixel into several independent components, determining three planesfor an RGB pseudo-color image, determining a sharpness factor plane,converting the RGB pseudo-color image to ahue-saturation-value/intensity (HSV/I) image having a plane, scaling thehue-saturation-value/intensity image plane with the sharpness factorplane, converting the hue-saturation-value/intensity image back to theRGB pseudo-color image, removing outliers beyond a standard deviationand stretching image between 0 and 1, displaying the region of interestin pseudo-colors; and characterizing a metabolic state of the tissue ofinterest.

The region of interest may be a pixel, a group of pixels in aprespecified region of a prespecified shape or a handoutlined shape oran entire field of view. Preferably, determining the three planes for anRGB pseudo-color image comprises one or more characteristic features ofthe spectra. Preferably, determining a sharpness factor plane comprisesa combination of the images at different wavelengths, preferably bytaking a ratio of a yellow plane in the range of about 550-580 nm to agreen plane in the range of about 495-525 nm, or by taking a combinationof oxyHb and deoxyHb spectral components, or by taking a ratio between awavelength in the red region in the range 615-710 nm and a wavelength inthe yellow region in the range of about 550-580 nm or in the orangeregion in the range of about 580-615 nm. Preferably, outliers areremoved beyond a standard deviation, preferably three standarddeviations. The region of interest is displayed in pseudo-colors,performed with one of in combination with a color photo image of asubject, or in addition to a color photo image of a subject, or byprojecting the pseudo-color image onto the observed surface.

Another embodiment of the invention is directed to a method forevaluating DFU or area of tissue at risk comprising preprocessing thehyperspectral information, building a visual image, defining a region ofinterest of the tissue, converting all hyperspectral image intensitiesinto units of optical density by taking a negative logarithm of eachdecimal base, decomposing a spectra for each pixel into severalindependent components, determining three planes for an RGB pseudo-colorimage, determining a sharpness factor plane, converting the RGB pseudocolor image to a hue-saturation-value/intensity (HSV/I) image having aplane, scaling the hue-saturation-value/intensity image plane with thesharpness factor plane, converting the hue-saturation-value/intensityimage back to the RGB pseudo-color image, removing outliers beyond astandard deviation and stretching image between 0 and 1, displaying theregion of interest in pseudo-colors, and characterizing a metabolicstate of the tissue of interest.

Another embodiment is directed to a medical instrument comprising animage projector, an illumination source, a remote control device and areal-time data processing package. Such a system could project thecolorized or other kind of image with relevant information back onto thetissue from which it was taken to assist the physician in diagnosis andtreatment such as wound debridement. Alternatively, information can betransmitted to the physician using multiple means, one of such can be aheads-up display.

Another embodiment is intended to help tell the doctor level ofamputation, safety of debriding tissue, likelihood for tissue to heal,selection and monitoring of specific therapy including topicalpharmaceuticals, skin-like coverings, vacuum suction apparatus, systemicpharmaceuticals, adequacy of surgical, stenting or atherectomyprocedure, extension of infection vs inflammation of tissue to assist intherapy, identification of organism responsible for local or systemicinfection.

Yet another embodiment can give information about tissue hydration andpotentially information about oxyHb and deoxyHb from deeper tissue usingNIR wavelengths. These can be used as a stand alone device or as pairedwith the more standard Visible wavelength MHSI device as shown in FIG.2.

Yet another embodiment can derive and present information from changesseen radiating from an area of wounded, ulcerated or otherwise abnormaltissue or from any change in tissue characteristics over a distance. A“gradient map” thus produced can be used to generate a diagnosis,predict the capability of the tissue to heal, define a level foramputation, define the infection vs inflammation, define areas ofischemia, define areas of tissue at risk for ulceration etc.

Another embodiment can involve dividing the region of interest intoradial segments, pie like segments or a combination of the two or intosquares or other geometric shapes and using these segments to compareand contrast different regions of tissue in the same field of view or ascompared to a similar field of view on the contralateral extremity or onanother part of the body (such as the forearm, the upper leg, etc.). Theradial segments can also be compared to similar locations at differenttime points to demonstrate change over time in response to differenttherapeutic interventions, changes in tissue physiology, either local,regional or systemic due either to progression or remission of diseaseor of the effects of topical or systemic medications or therapies.

Such measurements can be used to evaluate wound healing, tissueregeneration, angiogenesis, vasculogenesis, arteriogenesis, infection,inflammation, microvascular disease or alterations, or other changes intissue characteristics or physiology associated with the implementationof negative pressure (vacuum suction applied to the wound), hyperbarictherapy, grafting of autologuous, heterograft, xenograft or biologicalor synthetic skin substituetes, administration of topical agentsincluding antibiotics, cleansers, growth factors, surgical intervention,angioplasty, stenting, atherectomy, laser therapy, vasodilator therapy,offloading, compression, effects of pressure due to orthotic orprosthetic, effects of electromagnetic, acupuncture, massage, infrared,vibration or other therapies.

Such measurements can be considered as biomarkers representing tissueoxygen delivery and oxygen extraction tissue oxygenation, tissueperfusion, tissue metabolism or other characteristics correlated withMHSI measurements.

Such measurements can be used in association with the implementatiton ofhyperbaric therapy delivered to assist in the healing of ulceration indiabetic or other foot ulceration, or other wounds in other parts of thebody. In the case of hyperbaric oxygen therapy, the tissue can bemonitored before and at specified intervals during therapy orcontinuously during therapy to determine when the tissue has beenadequately modified (oxygenated) by the therapy or that there has beensufficient change in tissue metabolism as described by the MHSImeasurements of oxyHb, deoxyHb or other measured parameters or whetherno benefit is being delivered. MHSI can be used to determine theappropriate duration of HBO therapy during a given session and as towhether sufficient benefit has been delivered from a course of therapythat it can safely be discontinued and that the wound will then belikely to heal with more standard methods.

MHSI can be used to determine the capability of tissue to heat afterdebridement and hence the relative safety of pursuing such an approachSimilarly, MHSI can be used to help determine the lowest level ofamputation that can be performed with successful healing. Similarly MHSIcan be used to determine whether elective surgery to the foot, lowerextremity or other body part where evaluation and or quantitation ofperfusion, oxygenation, or tissue metabolism would assist indetermination of the safety of undertaking such a procedure or thelocation in which to direct such a procedure. MHSI can be utilizedbefore debridement, amputation or other surgery to make thisdetermination or during debridement, amputation/or other surgery tobetter assess tissue to improve surgical outcomes.

Such measurements can be used for the determination of which patients orwhich wounds are likely to improve with any of the above mentionedtherapies, which patients or wounds or portions of wounds are healing orworsening, when a given therapy is sufficient (this could be during orimmediately after application of a therapy such as hyperbaric therapy ora debridement or a particular cleansing or pharmaceutical regimen orafter a longer course of several days of therapy such as a vacuumtherapy. MHSI criteria can be used to determine when a tissue willaccept a skingraft or benefit from an allograft or other skinreplacement.

Systemic or Regional Disease

One embodiment uses a single system that employs light wavelengthsderived from the UV, visible, the near infrared, short wave infrared,mid infrared or far infrared portion of be electromagnetic spectrum.Another embodiment uses a system that uses one or more wavelengths frommore than one of these wavelength regimes. One such system usingwavelengths from more than one of these wavelength groupings is shown infigure two. In other embodiments, a single sensor could be used tocollect light from more than one wavelength regime.

A portable hyperspectral imaging apparatus according to an embodiment ofthe invention is depicted in FIG. 1. Portable apparatus 10 weighs lessthan 100 pounds, preferably less than 25 pounds, and more preferablyless than 10 pounds. Preferably, the portable apparatus may be batteryoperated, have some other form of portable power source or morepreferably, may have a connector adapted to connect to an existing powersource.

Portable apparatus 10 comprises an optical acquisition system 36 and adiagnostic processor 38. Optical acquisition system 36 comprises meansto acquire broadband data, visible data, ultraviolet data, infrareddata, hyperspectral data, or any combination thereof. In a preferredembodiment, optical acquiring means comprises a first-stage imagingoptic 40, a spectral separator 42, a second-stage optic 44, and animaging sensor 46. Alternatively, optical acquiring means may be anyacquisition system suited for acquiring broadband data, visible data,ultraviolet data, infrared data, hyperspectral data, or any combinationthereof. Preferably, one or more polarizers 41, 43 are included in theacquisition system to compile the light into a plane of polarizationbefore entering the imaging sensor. Preferably, a calibrator is alsoincluded in the system.

If the spectral separator 42 does not internally polarizes the light,the first polarizer 43 is placed anywhere in the optical path,preferably in front of the receiving camera 46. The second polarizer 41is placed in front of illuminating lights 20 such that the incidentlight polarization is controlled. The incident light is crossedpolarized with the light recorded by the camera 46 to reduce specularreflection or polarization at different angles to vary intensity of thereflected light recorded by the camera.

The illumination is provided by the remote light(s) 20, various sourcestailored or adapted to the need of the instrument, preferably positionedaround the light receiving opening of the system, or otherwise placed toafford optimal performance. The light can be a circular array of focusedLED lights that emit light at the particular wavelengths (or ranges)that are used in the processing algorithm, or in the ranges ofwavelengths (e.g., visible and/or near-infrared). The circulararrangement of the light sources provides even illumination that reducesshadowing. The light wavelength selectivity reduces effect of theobservation on the observing subject. The configuration may also varydepending on the particular needs and operation of the system.

Although the preferred embodiment describes the system as portable, anon-portable system may also be utilized. Preferably, an optical head ismounted to the wall of the examination room, more preferably, anoverhead light structure is located in the operating room, or morepreferably, the system has a portable table with an observational windowoverlooking the operating site.

The preferred embodiment may also be used as part of another instrument.For example, as an adjunct to an endoscope.

The first-stage optic receives light collected from a tissue samplethrough a polarizer and focuses the light onto the surface of thespectral separator. Preferably, the spectral separator is a liquidcrystal tunable filter (LCTF). LCTF 42 is a programmable filter thatsequentially provides light from selected wavelength bands with small(for example, 7-10 nm) bandwidth from the light collected from thesample. Second-stage optic 44 receives the narrow band of light passingthrough the spectral separator and focuses the light onto the imagesensor 46. The image sensor is preferably, although not necessarily, atwo-dimensional array sensor, such as a cargo-coupled device array (CCD)or CMOS, which delivers an image signal to the diagnostic processor 38.

Diagnostic processor 38 includes an image acquisition interface 50, thathas an input responsive to an output of the image sensor 46 and an outprovided to a general-purpose operating module 54. The general-purposeoperating module includes routines that perform image processing, andthat operates and controls the various parts of the system. Thegeneral-purpose operating module also controls the light source(s) (e.g.LED array) allowing for switching on and off during measurement asrequired by the algorithm. The general-purpose operating module hascontrol output provided to a filter control interface 52, which in turnhas an output provided to the spectral separator 42. The general-purposeoperating module also interacts with a number of diagnostic protocolmodules 56A, 56B, . . . 56N, and has an output provided to a videodisplay 12. The diagnostic process includes special purpose hardware,general-purpose hardware with special-purpose software, or a combinationof the two. The diagnostic processor also includes an input device 58,which is operatively connected to the general-purpose operating module.A storage device 60 and printer 62 also are operatively connected to thegeneral-purpose operating module.

In operation, a portable or semi-portable apparatus is employed withinline of site (or with optical access) of the object or area of interest,e.g. diabetic foot with or without an ulcer, or general area ofinterest. An operator begins by selecting a diagnostic protocol moduleusing the input device. Each diagnostic protocol module is adapted todetect particular tissue characteristics of the target. The diagnosticmodule could be specific for diabetes, for peripheral vascular disease,for venous stasis disease or for a combination of these disease states.As another example, a screening protocol for feet without ulcers or apotential for healing protocol for feet with ulcers. In an alternativeembodiment, the apparatus may contain only one diagnostic module adaptedfor general medical diagnosis.

Diagnostic processor 38 responds to the operator's input by obtaining aseries of transfer functions and an image processing protocol from theselected diagnostic protocol module 56. The diagnostic processorprovides the filtering transfer functions to the spectral separator 42via its filter control interface 52 and then instructs the imageacquisition interface 50 to acquire and store the resulting filteredimage from the image sensor 46. The general-purpose operating module 54repeats these filtering and acquiring steps one or more times, dependingon the number of filter transfer functions stored in the selecteddiagnostic protocol module. The filtering transfer functions canrepresent bandpass, multiple bandpass, or other filter characteristicsand can include wavelengths in preferably the UV, preferably thevisible, preferably the NIR and preferably, the IR electromagneticspectrum.

In a preferred embodiment, the light source delivering light to thetarget of interest can be filtered as opposed to the returned lightcollected by the detector. Thus, a tunable source delivers theinformation. Alternatively, both a tunable source and a tunable detectormay be utilized. Such tuning takes the form of LCTF, acousto-opticaltunable filter (AOTF), filter wheels, matched filters, diffractiongratings or other spectral separators. The light source may be atungsten halogen or xenon lamp, but is preferably a light emitting diode(LED).

The unique cool illumination provided by the LED prevents overheating ofskin which may result in poor imaging resolution. Preferably, the LEDprovides sufficient light while producing minimal or no increase in skintemperature. This lighting system in combination with the polarizeallows adequate illumination while preventing surface glare frominternal organs and overheating of skin. In certain embodiments,illumination can arise from more passive sources such as room lights orfrom sunlight.

Once the image acquisition interface 50 has stored images for all of theimage planes specified by the diagnostic protocol chosen by theoperator, the image acquisition interface begins processing these imageplanes based on the image processing protocol from the selecteddiagnostic protocol module. Processing operations can include generalimage processing of combined images, such as comparing the relativeamplitude of the collected light at different wavelengths, addingamplitudes of the collected light at different wavelengths, or computingother combinations of signals corresponding to the acquired planes. Thecomputed image is displayed on display 12. Other preferred embodimentsinclude storing the computed image in the storage device 60 or printingthe computed image out on printer 62.

In a preferred embodiment, a calibrator 65 is included in the system.Calibrator has an area colored with a pattern of two (or more) colors.To optimize use of the calibrator for this particular application whereoxyHb and deoxyHb are important components of the solution, colors arechosen that have a distinct absorption band in the wavelength rangesimilar to oxyHb and deoxyHb—preferably in the range 500-600 nm. Thecolors are placed into a pattern, preferably, a checker-board pattern,where 1 out of 4 squares has color1, and 3 out of 4 squares have color2.Thus, approximately 25% of the squares are color1 and 75% of the squaresare color2. The system takes a hypercube being slightly out offocus—that provides blurring of colors into each pixel. From the spectrafor each pixel, a linear composition of two spectra: one from color1 andanother from color2 are observed. The recorded spectra are decomposed ina manner similar to a system that decomposes skin spectra into oxyHb &deoxyHb components. However, in this instance it takes pure color1 andcolor2 spectra from library instead of oxyHb & deoxyHb. Validcalibration reports concentrations of 75% for color2 and 25% for color1.Results are similar to skin analysis, where the output is approximately90% of oxyHb and 10% of deoxyHb. Other embodiments include but are notlimited to, changes to the pattern, the color concentration & intensity,and the number of colors.

In summary, the system simulates the way the biological mixture(oxyHb+deoxyHb) is observed by using “optical” mixture via combinationof pattern (with known spatial concentrations) and analog blurring(defocusing—for speed. Defocusing can also be done in the softwarethrough the use of computational filters).

If the correct result is obtained, confirmation of the lightingdistribution and collection throughput, and the wavelength accuracy ofthe system given confidence in the spectra (wavelengths and intensity)that are being collected are provided. This provides additionalassurance that the data recorded off the patient is acceptable.

In another preferred embodiment, diagnostic protocol modules 56, printer62, display 12, or any combination thereof, may be omitted from portabledevice 10. In this embodiment, acquired images are stored in storagedevice 60 during the medical procedure. At a later time, these imagesare transferred via a communications link to a second device or computerlocated at a remote location, for example, hospital medical records, forbackup or reviewing at a later time. This second device can have theomitted diagnostic protocol modules, printer, display, or anycombination thereof. In another embodiment, the stored images aretransferred from portable device 10, located in the clinic, via acommunications link to a remote second device in real time.

In a preferred embodiment the system has facility to project real-timehyperspectral data onto the operation field, region of interest orviewing window positioned above the operating site. Also, the data canbe displayed completely separately for remote guidance (i.e. on a wallscreen for a group of people to review in real time, or post procedure).The projected information has precise one-to-one mapping to theilluminated surface (e.g. wound, operating surface, tissue) and providesthe surgeon or podiatrist with necessary information in efficient andnon-distractive way. When projected onto an overhang viewing window, theimages (real-color and/or pseudo-color) can be zoomed in/out to providevariable magnification. As illustrated in FIG. 1, the projectionsubsystem 70 includes the following elements: 1) image projector 71 withfield-of-view precisely co-aligned with the field-of-view of thehyperspectral imager, 2) miniature remote control device 72 which allowsthe surgeon or podiatrist to switch projected image on and off withoutturning from the site of debridement and change highlight structureand/or translucency on the projected image to improve visibility of thefeatures of interest as well as projected image brightness andintensity, 3) real-time data processing package 75 which constructsprojected image based on hyperspectral data and operator/surgeon input,4) optional viewing window 74 positioned above the operating site thatis translucent for real observation or opaque for projectingpseudo-color solution or higher resolution images.

The MHSI system consists of three functional modules—a Spectral Imager(SI), supporting Controller and Power Module (CPM) and Control and DataAcquisition Computer (CDAC). The MHSI also includes a thermometer thatremotely measures the temperature at the tissue surface. The SpectralImager is mounted on suspension arm which neutralizes device weight andallows for easy positioning and focusing of the instrument. Thesuspension arm is attached to wheeled cart which supports CPM and CDACas well. This configuration is very mobile and permits wide range ofdevice spatial and directional motions.

FIG. 2 shows the preferred system specifications along with a diagram ofour focusing methodology and the optical design of the Spectral Imager.In this embodiment, a liquid crystal tunable filters (LCTF's) was usedas the wavelength selector and are coupled to complementary metal oxidesemiconductor (CMOS) imaging sensors. Fitted with macro lenses and thepositional light focusing system described below, the system has apreferred working focal length of roughly 1 to 2 feet.

A major issue in the collection of hyperspectral imaging data is theposition and focusing of the instrument. While our Spectral ImagingModule is positioned on a ball joint that allows free rotation andvirtually any angle of incidence to the patient, it is imperative thatthere be a system in place for targeting the image to a particular spoton the tissue and ensuring that the instrument will be at the properdistance from the tissue to achieve optimal focus. Positioning andfocusing with our system are facilitated by two mirrored collimatedlight beams or lasers that cross precisely at the instrument focal plane(FIG. 2), and so bringing the spectral imaging module into positionwhere the two light spots overlap on the tissue to insure optimal focus.

To achieve precisely calibrated images, the system may use a speciallydesigned calibration pad placed at the focal plane of the system andmeasured prior to each patient measurement. The calibration pad includesa diffusely reflective surface to quantify the intensity of theillumination at each wavelength and color bars to validate wavelengthaccuracy of the system. Calibration data measured at a preset time suchas during maintenance calibrations can be stored and compared to witheach use to decide whether the system is within specifications andshould proceed to patient measurements.

To achieve precise co-registration between hyperspectral image andoperating surface, the system may use a fiducial label or target placedin the field of view which the image registration module can perform aself-alignment procedure before or during the operation as necessary.

Devices of the present invention allow for the creation and uniqueidentification of patterns in data that highlight the information ofinterest. The data sets in this case may be discrete images, eachtightly boded in spectra that can then be analyzed. This is analogous tolooking at a scene through various colored lenses, each filtering outall but a particular color, and then a recombining of these images intosomething new. Such techniques as fake color analysis (assigning newcolors to an image that don't represent the true color but are anartifact designed to improve the image analysis by a human) are alsoapplicable. Optionally, optics cat be modified to provide a zoomfunction, or to transition from a micro environment to a macroenvironment and a macro environment to a micro environment. Further,commercially available features can be added to provide real-time ornear real-time functioning. Data analysis can be enhanced bytriangulation with two or more optical acquisition systems. Polarizationnay be used as desired to enhance signatures for various targets.

In addition to having the ability to gather data, the present inventionalso encompasses the ability to combine the data in various mannersincluding vision fusion, summation, subtraction and other, more complexprocesses whereby certain unique signatures for, information of interestcan be defined so that background data and imagery can be removed,thereby highlighting features or information of interest. This can alsobe combined with automated ways of noting or highlighting items, areasor information of interest in the display of the information.

The hyperspectrally resolved image in the present invention is comprisedof a plurality of spectral bands. Each spectral band is adjacent toanother forming a continuous set. Preferably, each spectral band havinga bandwidth of less than 50 nm, more preferably less than 30 nm, morepreferably less than 20 nm, more preferably, from about 20-40 nm morepreferably, from about 20-30 nm, more preferably, from about 10-20 nm,more preferably from about 10-15 nm, and more preferably from about 5-12nm.

It is clear to one skilled in the art that there are many uses for amedical hyperspectral imager (MHSI) according to the invention. The MHSIoffers the advantages of performing the functions for such uses faster,more economically, and with less equipment and infrastructure/logisticstail than other conventional techniques. Many similar examples can beascertained by one of ordinary skill in the art from this disclosure forcircumstance where medical personal relies on their visual analysis ofthe biological system. The MHSI acts like “magic glasses” to help humanto see inside and beyond.

Algorithm Description

The embodiment of diabetes algorithm involves the following steps:

-   1. Preprocess the MHSI data. Preferably, by removing background    radiation by subtracting the calibrated background radiation from    each newly acquired image while accounting for uneven light    distribution by dividing each image by the reflectance calibrator    image and registering images across a hyperspectral cube.-   2. Build a color-photo-quality visual image. Preferably, by    concatenating three planes from the hyperspectral cube at the    wavelengths that approximately correspond to red (preferably in the    range of about 580-800 nm, more preferably in the range of about    600-700 nm, more preferably in the range of about 625-675 nm and    more preferably at about 650 nm), green (preferably in the range of    about 480-580 nm, more preferably in the range of about 500-550 nm,    more preferably in the range of about 505-515 nm, and more    preferably at about 510 nm), and blue (preferably in the range of    about 350-490 nm, more preferably in the range of about 400-480 nm,    more preferably in the range of about 450-475 nm, and more    preferably at about 470 nm) color along the third dimension to be    scaled for RGB image.-   3. Define a region of interest (ROI), preferably, where the solution    is to be calculated unless the entire field of view to be analyzed.-   4. Convert all hyperspectral image intensities into units of optical    density. Preferably, by taking the negative logarithm of the decimal    base. FIG. 2 shows examples of spectra taking from single pixels at    different tissue sites within an image. Tissue sites include    connective tissues, oxygenated tissues, muscle, tumor, and blood.-   5. Decompose the spectra for each pixel (or ROI averaged across    several pixels). Preferably, decompose into several independent    components, more preferably, two of which are oxyhermoglobin and    deoxyhemoglobin.-   6. Determine three planes for pseudo-color image. Preferably, define    the color hue plane as apparent concentration of oxygenated Hb, or    deoxygenated Hb, or their mathematical combination, e.g. total Hb,    oxygen saturation, etc. Preferably, define the color saturation    plane as apparent concentration of oxygenated Hb, or deoxygenated    Hb, or their mathematical combination, e.g. total Hb, oxygen    saturation, etc. Preferably, define the color intensity (value)    plane as reflectance in blue-green-orange region (preferably in the    range of light at about 450-580 nm).-   7. Adjust the color resolution of the pseudo-color image according    to quality of apparent concentration of oxygenated Hb, or    deoxygenated Hb, or their mathematical combination, e.g. total Hb,    oxygen saturation, etc. Preferably, reduce resolution of hue and    saturation color planes by binning the image (e.g. by 2, 3, 4, etc.    pixels); or/and by resizing the image, or/and by smoothing the image    through filtering higher frequency components out. Interpolate the    smoothed color planes on the grid of higher resolution intensity    (value) plane.-   8. Convert hue-saturation-value/intensity (HSV/I) image to    red-green-blue (RGB) image.-   9. Remove outliers in the resulting image, defining an outlier as    color intensity deviating from a typical range beyond certain number    of standard deviations, preferably three. Stretch the resulting    image to fill entire color intensity range, e.g. between 0 and 1 for    a double precision image.-   10. Display ROI in pseudo-colors, preferably, in combination with    the color photo image of the subject, or preferably, in addition to    the color photo image of the subject, or more preferably, by    projecting the pseudo-color image onto the observed surface.    Additional information can be conveyed through images portraying the    individual coefficients from oxyHb, deoxyHb, slope and offset    coefficients, or any linear or nonlinear combination such as the    oxyhemoglobin to deoxyhemoglobin ratio.-   11. Characterize the metabolic state of the tissue of interest (e.g.    risk for ulceration, potential to heal). Preferably, by using the    saturation and/or intensity of the assigned color and provide a    qualitative color scale bar.

As is clear to a person of ordinary skill in the art, one or more of theabove steps in the algorithm can be performed in a different order oreliminated entirely and still produce adequate and desired results.Preferably, the set of instructions includes only the steps ofpreprocessing the hyperspectral information, building a visual image,using the entire field of view, converting all hyperspectral imageintensities into units of optical density by taking a negative logarithmof each decimal base, and characterizing a metabolic state of the tissueof interest. More preferably, the set of instructions comprisespreprocessing the hyperspectral information, defining a region ofinterest of the tissue, and characterizing a state of the tissue ofinterest.

Another preferred embodiment entails reducing the hyperspectral data inthe spectral dimension into a small set of physiologic parametersinvolves resolving the spectral images into several linearly independentimages (e.g. oxyhemoglobin, deoxyhemoglobin, an offset coefficientencompassing multiple scattering (MS) properties and a slopecoefficient) in the visible regime. Another embodiment determines fourimages (e.g. oxyhemoglobin, deoxyhemoglobin, offset/scatteringcoefficient, and water absorption) in the near infrared region of thespectrum. As an example for the visible region of the spectrum, linearregression fit coefficients c1, c2, c3 and c4 will be calculated forreference oxy-Hb, deoxy-Hb, and MS spectra, respectively, for eachspectrum (Sij) in an image cue:{right arrow over (S)} _(ij) =∥c ₁ {right arrow over (OxyHb)}+c ₂ {rightarrow over (DeoxyHb)}+c ₃{right arrow over (Offset+c ₄Slope)}∥₂

Individual images of the oxyhemoglobin and deoxyhemoglobin components,the slope and offset or any combination, linear or nonlinear, of theseterms, for example the oxy- to deoxyhemoglobin ratio, can be presentedin addition to producing the pseudo-colored image to the user.

In order to present the MHSI effectively, a display method was developedthat has the potential to convey a 2-dimensional index, and convey thevalues for both the oxy and deoxyhemoglobin coefficients independently.The method of displaying our index uses a color scale, in one iterationthis ranges from purple values (high) to brown values (low) to indicatethe concentration of oxyhemoglobin in the tissue, and a brightnessscale, ranging from very bright (high) to faded (low) associated withthe tissue concentration of deoxyhemoglobin. FIG. 3 summarizes thedisplay of the MHSI, showing a schematic diagram explaining thescenarios of low and high oxy and deoxy hemoglobin coefficients as wellas a color scale that indicates a color plat that shows the verticalcolor scale and the horizontal brightness scale. By measuring an MHSIwhere the oxyhemoglobin component is high and the deoxyhemoglobincomponent is low (upper left hand corner of FIG. 3), it could beconcluded that that particular area of tissue has adequate perfusion andoxygenation, and is able to satisfy its metabolic needs with the oxygenthat is being delivered. That this tissue has the lowest level of riskfor ulceration and the highest probability of healing. If tissuedemonstrates a low oxyhemoglobin level in addition to a lowdeoxyhemoglobin level (lower left corner of FIG. 3), this would implythat the tissue was receiving low total volume of blood. If tissuedemonstrates a low oxyhemoglobin level in addition to a highdeoxyhemoglobin level (lower right corner of FIG. 3) this would implythat the tissue has metabolic requirements exceeding available oxygendelivery. In both of these regions there is expected to be a higher riskof ulceration or difficulties with wound healing. If the tissue has ahigh oxyhemoglobin coefficient and also has a high deoxyhemoglobincontent, (lower left corner of FIG. 3) this tissue was receiving alarger total volume of blood, and that the oxygen extracted from theblood stream was adequate to support tissue metabolism. This could beindicative of inflammation. Our technique will uniquely permitdiscrimination between each of these disparate physiologic conditions.For example, if the value is faded purple (upper left hand quadrant) thetissue has very high oxygenation, as discussed above, and is very likelyto heal. The color map (right) gives an indication of how the MHSI wouldbe represented in an image format.

Described here is hyperspectral imaging for use in the peripheralvascular and diabetes clinic, designed both to be mobile for ease of useand to facilitate the most accurate data collection possible. Thissystem provides fast and precise measurement of reflectance spectra, andis characterized by high spatial and spectral resolution, as well as theability to process spectral data in real time. It has been equipped witha turn-key software interface for the user. Proprietary imageregistration software insures image stability when measuring spectra ofanimated objects. The system does not rely on external illumination,rather it contains very efficient internal visible (and NIR in certainversions) light sources, which allow for achieving high signal to noiseratios in measured data without putting noticeable heat load on abiological subject (variations in skin temperature during acquisitionare on the order of 0.1 C).

All MHSI data were corrected for background and uneven illumination, andnormalized by the integration time. The data were ratioed to thereflectance of a calibration standard, and negative decimal logarithmwas taken to obtain the absorption data. Images at all wavelengths wereco-registered using proprietary software developed by HYPERMED to ensurethat each pixel represents the same point on the skin throughout allwavelengths. The spectra were then deconvolved into fourlinearly-independent spectral components with coefficients representingthe amount of hemoglobin (both oxyHb and deoxyHb) in the observed skin.Typically two numbers are presented x/y wherein x represents oxyHb and yis deoxyHb. The values for x and y can be taken from a single pixel orfrom a ROI defined by the user. In addition the hemoglobin oxygensaturation (S_(HSI)O₂), x/(x+y), can be presented for a pixel or a ROI.FIG. 4 shows examples of tissue with low and high oxyHb and deoxyHbvalues corresponding to tissue at risk of ulceration and a wound that islikely to heal, respectively. Another way of presenting linearly indentvariables is through their sum and difference: (x+y) and (x−y). Thefirst would be THb, and the second would “hint” on oxygenextraction—which indicates the kind of Hb that is predominant at thesite.

Data in the following table represent typical oxyHb, deoxyHb, andS_(HSI)O₂ values for two body positions, forearm and foot, and forvarious stages of diabetes: nondiabetics, diabetics without peripheralneuropathy, and diabetics with peripheral neuropathy. In general, thevalue for oxyHb and S_(HSI)O₂ are lower in the feet of diabetic subjectswith neuropathy compared to the other two groups, a group at high riskfor developing foot ulcers. In addition, the values for oxyHb, deoxyHb,and S_(HSI)O₂ depend on body location, that once calibrated can beaccounted for by the diagnostic module.

MHSI oximetry values at baseline (prior to iontophoresis ofacetylcholine) Site Group (N) Oxy Deoxy S_(HSI)O₂ (%) Forearm Control(21) 29 ± 7* 41 ± 16  42 ± 17** Diabetic Non- 20 ± 5  44 ± 10  32 ± 8**Neuropathic (36) Diabetic 19 ± 7  49 ± 10  28 ± 8** Neuropathic (51)Dorsum Control (21) 25 ± 13 44 ± 18 38 ± 22 of foot Diabetic Non- 24 ±9  41 ± 11 37 ± 12 Neuropathic (36) Diabetic  19 ± 9*** 45 ± 13   30 ±12**** Neuropathic (51) *p < 0.0001 compared to diabetics with andwithout neuropathy **p < 0.0001 for all three groups ***p < 0.025 whencompared to control and nonneoropathic ****p < 0.027 when compared tocontrol and nonneoropathic

In summarizing these data, MHSI provides relevant physiologicalinformation at the systemic, regional and local levels. Forearm datameasures systemic microvasculature changes since the forearm is notaffected by macrovasculature or somatic neuropathy as found in the lowerextremities. Dorsal foot measurements are indicative of microvascularand macrovascular effects including atherosclerotic changes occurring inlarge vessels exacerbated by diabetes. MHSI data from the right and leftlower extremity can be compared to help differentiate the stages of thedamage. Finally, MHSI can be used to find local information that can beassociated to the risk of developing a foot ulcer of the progression ofdisease by examining the area around an ulcer.

MHSI can not only be used for determining risk of foot ulceration, butalso for determining systemic progression of diabetic microvasculardisease. In one embodiment this is determined by mean oxyHb, deoxyHband/or other values for a region of interest. In another embodiment thisis determined by heterogeneity of oxyHb, deoxyHb and/or other values fora region of interest. In another embodiment this is determined by thepatterning of oxyHb, deoxyHb and/or other values for a region ofinterest. In other embodiments this is determined by changes over agiven time period within a measurement session (between 1 picosecond andone hour, preferably between 100 microseconds and 10 minutes and morepreferably between 100 microseconds and 15 seconds) and in the meanvalues or patterns of oxyHb, deoxyHb and/or other values for a region ofinterest. These measurements can be used to determine a diabetesprogression index (DPI). Alternatively, a DPI can be calculated bycomparing a MHSI value or set of values from a single point in time withanother point in time (preferably 1 month to two years, more preferably2 months to one year and most preferably 3-6 months)

Using the active stimulus of acetylcholine as a vasodilator, and theknown effects of this on LD measurements data was derived in whichchanges in MHSI could be observed under known alterations in physiologyand compare these with baseline images and with LD data (FIG. 5). Usingdata collected from diabetic patients, as well as previous data fromhuman shock studies and iontophoresis studies, an algorithm was derivedthat clearly discriminates regions vasodilated by iontophoresis and alsodiscriminates ulcer from non ulcer with a proprietary formula thatincludes terms for oxyHb and deoxyHb. This was further developed as aHyperspectral Microvascular Index (HMI), which is a metric of tissuephysiology and have explored the use of the MHSI in evaluating tissue ofthe foot In circumstances when an ulcer has been present, tissue wasexamined within the ulcer, directly adjacent to the ulcer, surroundingthe ulcer and at various other regions of the foot.

With the aid of MHSI, a quantitative metric is demons with superbseparation between ulcerated or wounded and non-ulcerated or woundedtissue. Areas of different tissue metabolism can be seen with 60 micron(20-120) spatial resolution. Regions with an increased MHSI associatedwith the margins of the ulcer can be seen which correlate toinflammation (and/or infection). Areas of decreased MHSI can be seen inother areas which from previous work in ischemia is considered to betissue at risk for non-healing, ulcer extension, or primary ulceration.These data validate the capability of our measurement system to have theresolution and appropriate range to quantitatively assess differentareas of tissue metabolism on both dorsal and plantar foot surfaces aswell as skin on other body areas or other tissues visible throughendoscopic techniques or at the time of open surgery of the foot, leg,arm or any other body part including internal organs at laparoscopy orthe retina at retinoscopy. The invention provides the capability toperform this quantitative assessment on tissue that demonstrates novisible differences on clinical examination to the skilled examiner.

MSHI images have the ability to differentiate between regions of tissueassociated with a present foot ulcer on the basis of biomarkers such asthe oxyHb and deoxyHb coefficients. FIG. 6 shows an ulcer on the sole ofthe foot of a type 1 diabetic patient (ulcer 1). From the visible imageon the left, little distinguishes one area of the ulcer from another.However when looking at the image with the MHSI, there is obviousdiscriminatory power between the state of tissue seen in the purpleoval, which is likely to heal, and that surrounded by the black oval,which is tissue at risk for further ulceration. It is important to notethat the skin on the sole of this patient's feet is highly calloused,with a thick stratum corneum, but one is still able to differentiatetissue based on its spectral signatures. Given that the sole of the footis often the site of the thickest stratum corneum on the body, thedevice works on all naturally or surgically exposed tissue or tissueotherwise visualized with laparoscopy, endoscopy, retinoscopy or othervisualization techniques. Ulcer 2 was located on the dorsal surface ofthe foot, on the patient's big toe (FIG. 6). These images further showthe ability to differentiate between tissue at risk and tissue likely toheal. Additionally, tissue surrounding a fungal infection on thepatient's middle toe (bottom right-band corner of the image) has an MHSIthat can demonstrate inflamed or infected tissue.

In addition to the differentiation of local tissue, tissue can beexamined for gross features indicative of global risks of complications,such as poor perfusion or the inability of the microcirculation to reactand compensate in tissue. In another embodiment, iontophoreticapplication of the vasodilator acetylcholine (ACH) or nitroprusside wasused to stimulate the vasodilation of the microvasculature on the dorsalsurface of the foot and on the forearm of the patients and measured thereaction with MHSI (FIG. 7).

The potential of hyperspectral imaging in diagnosing globalmicrocirculatory insufficiencies and impacting on other complications ofdiabetes associated with the microvasculature besides foot ulcers. InFIG. 7, hyperspectral measurements from the feet of four patients, withthe first two columns of images showing the MHSI of the soles of bothfeet, and the second two columns showing images of the dorsal surfacesof both feet after the application of ACH via iontophoresis. In thefirst three patients, an MHSI is seen that is much healthier than thatof the fourth patient. Consequently, the fourth patient had a foot ulcerat the time of this study and has a previous history of ulceration.While the contrast between the data from the soles in these patients issting, there is complementary information in the data from themicrovascular response shown in the two columns on the right. Note thatthe first three patients all have MHSI scores that contain purpleinformation in response to vasodilation, while the fourth patient showswhat would be considered an MHSI that was indicative of tissue that wasat risk. Microcirculatory changes associated with the progression ofdiabetes can also be modified by different treatment and therapeuticregimens and with the overlay of other systemic diseases (such ascongestive heart failure or hypertension) or treatments or therapies forsystemic diseases.

To analyze the ulcer data further, ulcer images were divided into 25concentric circles 1 mm apart and 8 pie segments forming 200 sectors perulcer (FIG. 8). A radial profile analysis was undertaken where the ulcercenter was defined at the first visit, and registered images fromsubsequent visits to this. OxyHb, deoxyHb, total-hemoglobin and O₂Satwere calculated for each sector.

Each radial pie segment was evaluated for signs of healing, nonhealingor progression in subsequent visits. MHSI measurements and clinicalhealing results were compared. MHSI algorithms were developed toidentify changes associated with ulcer healing, nonhealing andprogression. A primary endpoint evaluated the specific sectors of tissuearound an ulcer that would heal, not heal or progress. The groupestimates for oxyHb, deoxyHb, and O₂Sat are given in the following tableusing a linear mixed effects regression model. Significant differenceswere seen for healing for the oxyHb and deoxyHb values. Patients who didnot heal also demonstrated increased heterogeneity in distant foot andin arm measurements. For the 21 ulcers studied, the algorithm predicted6 of 7 ulcers that did not heal and 10 of 14 ulcers that healed.

Conclusion: MHSI identifies microvascular abnormalities in the diabeticfoot and provides early information assist in managing foot ulcerationand predict outcomes in patients with diabetes.

Group Estimates (±SEM) MHSI Not Healing Healing p-value OxyHb 36.4 ± 2.251.9 ± 1.8 <.0001 DeoxyHb 34.2 ± 1.9 47.8 ± 1.6 <.0001 S_(HSI)O₂  0.51 ±0.01  0.51 ± 0.01 0.8646

MHSI is used to monitor angiogenesis during wound healing. An example ofwound healing in a diabetic rabbit wound model shows that during thehealing process, images of oxyHb and deoxyHb show patterns that changein shape, area, and amplitude with time. Similar patterns were noted inexperimental models of shock, but the changes observed for shockoccurred on a shorter time scale; minutes rather than several days asthe wound heals. The rabbit's ears were observed at days 1, 2, 5, and10. MHSI is ideally suited for characterization of the localheterogeneity in oxyHb and deoxyHb and their spatial changes with time.For example, the zone of hyperemia surrounding a wound as measured bythe oxyHb coefficient decreases with time in wounds that heal (FIG. 9).The color image (a), reconstructed from MHSI data, shows a part of theobserved area 50-by-40 mm, recorded at the baseline on day 1. The blackrings denote location of a future wound. The pseudocolor image (b),obtained as a result of hyperspectral processing, shows distribution ofthe oxyHb and deoxyHb in the underlying tissue at the same time. Thecolor hue represents apparent oxyHb concentrations, whereas colorsaturation (from fade to bright) represents apparent deoxyHbconcentrations. Both, oxyHb and deoxyHb vary predominantly between 40and 90 MHSI units (color bar to the right). The remaining images to theright show change in a region of interest 17-by-17 mm (black box in (a)and (b)) over 10 days. At day 2, the oxy concentrations increasedsignificantly in the area as far as 10 mm away from the wound border. Byday 5, the increase in oxygenation became more local (purple area,shrunken to about 5 mm) and new microvasculature formed to feed the areain need (red fork-like vessels in the right top corners appearing indays 5 and 10 images). By the 10^(th) day, the area of increased oxyHbhas not changed much, but the peak in oxy amplitude decreased,suggesting a period of steady healing.

As depicted in FIG. 10, 50-micron resolution images of a rabbit's earwere taken with MHSI over a ten day period. In FIG. 10( a), the colorimage was reconstructed from MHSI data, showing a party of the observedarea 50-by-40 mm, recorded at the baseline on day 1. The pseudo-image(b) was obtained as a result of hyperspectral processing showing adistribution of the oxygenated (oxy) and deoxygenated (deoxy) hemoglobinin the underlying tissue at the same time.

Other embodiments and uses of the invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the invention disclosed herein. All references cited herein,including all publications, U.S. and foreign patents, and patent andprovisional applications, and all publications and documents citedherein for any reason, are specifically and entirely incorporated byreference. It is intended that the specification and examples beconsidered exemplary only.

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1. A medical instrument comprising: a first stage optic configured toreceive light from tissue of a subject, the light containing informationabout a vascular condition of the tissue; a spectral separatorconfigured to filter light received from the first stage optic; animaging sensor configured to receive filtered light from the spectralseparator and to generate an image of the tissue based on the filteredlight; one or more polarizers positioned between the tissue and theimaging sensor and configured to polarize the light received by theimaging sensor; and a diagnostic processor, comprising: a filter controlinterface operatively connected to the spectral separator; an imageacquisition interface operatively coupled to the imaging sensor; adiagnostic module containing information about a plurality of bandwidthsof light selected to characterize the vascular condition of the tissue;and a general purpose operating module operatively connected to thefilter control interface, the image acquisition interface, and thediagnostic module, the general purpose operating module configured toinstruct, based on the diagnostic module, the filter control interfaceto cause the spectral separator to sequentially filter the lightreceived from the first stage optic in each bandwidth of the pluralityof bandwidths, the general purpose operating module further configuredto instruct, based on the diagnostic module, the image acquisitioninterface to obtain from the image sensor a sequence of images, eachimage corresponding to a bandwidth of the plurality of bandwidths, thegeneral purpose operating module further configured to generate, basedon the sequence of images, a two-dimensional index characterizing thevascular condition of the tissue, wherein the two-dimensional indexincludes a first scale to represent a concentration of oxyhemoglobin inthe tissue, and a second scale to indicate a concentration ofdeoxyhemoglobin in the tissue and wherein corresponding pixels in eachimage in the sequence of images are co-registered to derive acoefficient for oxyhemoglobin and a coefficient for deoxyhemoglobin fromeach set of co-registered pixels in the sequence of images, and thecoefficient for oxyhemoglobin and the coefficient for deoxyhemoglobinfrom each set of co-registered pixels in the sequence of images isindependently displayed with the two-dimensional index thereby conveyingspatial information about oxyhemoglobin concentration anddeoxyhemoglobin concentration in the tissue.
 2. The medical instrumentof claim 1 further comprising a second stage optic configured to focusthe filtered light onto the imaging sensor.
 3. The medical instrument ofclaim 1 wherein the medical instrument is affixed to the subject totrack said state of the tissue over time.
 4. The medical instrument ofclaim 1 further comprising at least one of an image projector, anillumination source, a remote control device, a real-time dataprocessing package, a receiving camera, a calibrator, or a combinationthereof.
 5. The medical instrument of claim 4 wherein the illuminationsource comprises a circular array of focused LED lights operativelyconnected to the general purpose operating module.
 6. The medicalinstrument of claim 4 wherein the image projector is operativelyconnected to the general purpose operating module and is configured toproject an image containing information about the vascular condition ofthe tissue onto the tissue to assist a physician in diagnosis andtreatment of said tissue.
 7. The medical instrument of claim 1 whereinthe first stage optic focuses the light received from the tissue onto asurface of the spectral separator.
 8. The medical instrument of claim 1wherein the spectral separator comprises a programmable liquid crystaltunable filter.
 9. The medical instrument of claim 1 wherein eachbandwidth of the plurality of bandwidths is between 7 and 10 nm wide.10. The medical instrument of claim 1 wherein the diagnostic processorcomprises a plurality of diagnostic protocol modules, each of which areadapted to detect specific characteristics of the tissue.
 11. Themedical instrument of claim 1, wherein the first scale is a color scaleand the second scale is a brightness scale.
 12. The medical instrumentof claim 1, further comprising two mirrored collimated light beams orlasers that cross at a focal plane of the imaging sensor so that theimaging sensor is focused when the two light spots generated from thetwo mirrored collimated light beams or lasers overlap on the tissue. 13.The medical instrument of claim 1, wherein the tissue is peripheraltissue.
 14. A method for assessing a vascular condition of tissue of apatient, the method comprising: selecting a diagnostic protocol modulefrom among a plurality of diagnostic protocol modules, the selecteddiagnostic protocol module containing information about a plurality ofbandwidths of light selected to characterize the vascular condition ofthe tissue; receiving light from the tissue, the light containinginformation about the vascular condition of the tissue; filtering thereceived light in each bandwidth of the plurality of bandwidths;obtaining, from one or more image sensors, a sequence of images, eachimage corresponding to a bandwidth of the plurality of bandwidths; andgenerating based on the sequence of images, with a general purposeoperating module, a two-dimensional index characterizing the vascularcondition of the tissue, wherein the two-dimensional index includes afirst scale to represent a concentration of oxyhemoglobin in the tissue,and a second scale to indicate a concentration of deoxyhemoglobin in thetissue and wherein corresponding pixels in each image in the sequence ofimages are co-registered to derive a coefficient for oxyhemoglobin and acoefficient for deoxyhemoglobin from each set of co-registered pixels inthe sequence of images, and the coefficient for oxyhemoglobin and thecoefficient for deoxyhemoglobin from each set of co-registered pixels inthe sequence of images is independently displayed with thetwo-dimensional index thereby conveying spatial information aboutoxyhemoglobin concentration and deoxyhemoglobin concentration in thetissue.
 15. The method of claim 14 wherein generating thetwo-dimensional index comprises at least one of comparing a relativeamplitude of filtered light in different wavelength bands, addingamplitudes of filtered light in different wavelength bands, computing acombination of signals, or a combination thereof.
 16. The method ofclaim 14 further comprising calibrating an image acquisition interfacefor an absorption band in a wavelength range similar to oxyHb ordeoxyHb.
 17. The method of claim 16 wherein the wavelength range isbetween about 500 and 600 nm.
 18. The method of claim 14 furthercomprising projecting multispectral or hyperspectral information onto anoperation field, a region of interest, or a viewing window positionedabove an operating site.
 19. The method of claim 18 wherein theprojected multispectral or hyperspectral information has preciseone-to-one mapping to the tissue and assists a physician in diagnosisand treatment of said tissue.
 20. The method of claim 18 wherein theprojected multispectral or hyperspectral information exhibits real orpseudo color and can be zoomed in or out to provide variablemagnification.
 21. The method of claim 14 wherein each of the selecteddiagnostic protocol modules is adapted to detect specificcharacteristics of the tissue.
 22. The method of claim 21 furthercomprising evaluating, based on the two-dimensional index, at least oneof wound healing; tissue regeneration; angiogenesis; vasculogenesis;arteriogenesis; infection; inflammation; microvascular disease oralteration; changes in tissue characteristics or physiology associatedwith implementation of negative pressure; hyperbaric therapy;administration of topical agents including antibiotics, cleansers, orgrowth factors; surgical intervention; angioplasty; stenting;atherectomy; laser therapy; vasodilator therapy; compression; effects ofelectromagnetic, acupuncture, massage, infrared, or vibration therapies,diabetes, peripheral vascular disease, venous stasis disease, or acombination thereof.
 23. The method of claim 14, wherein the first scaleis a color scale and the second scale is a brightness scale.
 24. Themethod of claim 14, wherein the tissue is peripheral tissue.